Exception Handling

[Marie Jeanne Thibault]

Hi Everyone,
I'm wondering if you can help me with this...I want a message to be displayed if args[1] and args[2] are anything but integers. I know my "if" statements are not right but that's what I want it to do. How do I make this work? Here's my code...
//ExceptDemo1a.java
public class ExceptDemo1a
{
//Main Method with three arguments
//args[0]: operator
//args[1]: operand1
//args[2]: operand2
public static void main(String[] args)
{
//Declare and initialize variables
int result = 0;
int operand1 = 0;
int operand2 = 0;
if(operand1 != int)
{
operand1 = new Integer(args[1]).intValue();
try
{
switch (args[0].charAt(0))
{
case '+': result = Integer.parseInt(args[1]) +
Integer.parseInt(args[2]);
break;
case '-': result = Integer.parseInt(args[1]) +
Integer.parseInt(args[2]);
break;

case '*': result = Integer.parseInt(args[1]) +
Integer.parseInt(args[2]);
break;
case '/': result = Integer.parseInt(args[1]) +
Integer.parseInt(args[2]);
}
}
catch(Exception ex1)
{
System.out.println("Input must be an integer");
}
}

else if(operand2 != int)
{
operand2 = new Integer(args[2]).intValue();
try
{
switch (args[0].charAt(0))
{
case '+': result = Integer.parseInt(args[1]) +
Integer.parseInt(args[2]);
break;
case '-': result = Integer.parseInt(args[1]) +
Integer.parseInt(args[2]);
break;

case '*': result = Integer.parseInt(args[1]) +
Integer.parseInt(args[2]);
break;
case '/': result = Integer.parseInt(args[1]) +
Integer.parseInt(args[2]);
}
}
catch(Exception ex2)
{
System.out.println("Input must be an integer");
}
}

//Display the result
System.out.println(args[1]+ ' ' +args[0]+ ' ' +args[2]+ "=" +result);
}
}

Any help would sure be appreciated!!!
Thanks,
Marie

[karl koch]

hi

you can use a try/catch block because the parseInt method throws a NumberFormatException:

 
try {
  int operand1 = Integer.parseInt(args[1]);
  int operand2 = Integer.parseInt(args[2]);
  ....
  switch() {
  .....  
  }
  .....
  System.out.println("result = " .....);
  .....
}catch(NumberFormatException nfe) {
  // at least one argument was not an int
  // show your message
  ....
}

- you can use 'operand1' and 'operand2' in your switch statement (should make the code a bit more readable) instead of the Integer.parseInt() statements.
- you should check if the args array has the good length
- you can also check if the operator is valid

cheers and a happy new year
K

[Marie Jeanne Thibault]

Thanks Karl, worked like a charm.
Marie